Aqueous emulsions, a process for the preparation and the use thereof

ABSTRACT

The invention relates to aqueous emulsions, a process for the preparation and the use thereof.

[0001] Organopolysiloxane preparations cross-linking by hydrosilylationreactions have long been used as emulsions for e.g. release coatings forflexible materials (U.S. Pat. No. 3,527,659). Such cross-linking systemsgenerally comprise:

[0002] at least one organopolysiloxane with at least two unsaturatedhydrocarbon groups in the molecule,

[0003] at least one organohydrogen polysiloxane with at least three SiHgroups in the molecule, and

[0004] a quantity of a metal compound from the platinum group sufficientfor a catalytic effect.

[0005] Moreover, two-component emulsion systems are used for thepreparation of release coatings which, according to U.S. Pat. No.3,900,617, are composed of a 40% emulsion of a dimethylpolysiloxanepolymer with dimethylvinylsiloxy end groups, a Pt catalyst, emulsifiersin water and a 40% emulsion of a methyl hydrogen polysiloxane.

[0006] Said emulsion systems still have an unsatisfactory releaseperformance, however.

[0007] The problem of storage stability which occurs with many emulsionswas solved in U.S. Pat. No. 5,500,148 by the fact that the pH of theemulsion is adjusted to 3 to 5 by means of an organic or inorganic acid.Here, too, however, it is still necessary to add the Pt catalyst to themixture of the other components immediately before the emulsion is usedin order to ensure that the curing reaction takes place.

[0008] Now as ever, a difficulty with the preparation of releasecoatings is that of obtaining the suitable pot lives, i.e. the residencetimes of the substrates to be coated in the bath containing the siliconecoating and guaranteeing rapid curing in the drying oven. Gel particles,i.e. cured silicone particles, often form in the oven itself with theemulsions known hitherto for the release coating. This phenomenon, knownas dusting, reduces the yield of silicone applied to the substrate andrequires an immense amount of cleaning from time to time in the regionof the drying oven and its surroundings. Another disadvantage of theemulsions known from the prior art is that of intense foaming, which isa troublesome feature during processing.

[0009] The object of the present invention was, therefore, to provideaqueous emulsions which are suitable for the preparation of an abhesive(release) finish for flexible substrates, particularly as a releasecoating, and which do not exhibit the disadvantages known in the priorart.

[0010] Surprisingly, it has now been found that aqueous emulsions whichcontain addition-cross-linking polydiorganosiloxanes and smallquantities of unreactive organopolysiloxane in addition to the knownconstituents are easy to prepare and stable in storage, in which dustingmay be very largely avoided in high-quality coatings and in whichfoaming may also be very largely suppressed.

[0011] The invention therefore provides aqueous emulsions consistingessentially of:

[0012] at least one organopolysiloxane A) containing at least 2unsaturated hydrocarbon groups,

[0013] at least one methyl hydrogen polysiloxane B),

[0014] at least one unreactive organopolysiloxane C),

[0015] at least one catalyst D) from the platinum group,

[0016] at least one inhibitor E),

[0017] optionally, emulsifiers and/or thickeners F), and

[0018] optionally, additives and/or auxiliary substances G).

[0019] The organopolysiloxane A) within the meaning of the inventioncontaining at least 2 unsaturated hydrocarbon groups is preferably acyclic, linear or branched polysiloxane which has units corresponding tothe general formula

(R)_(a)(R¹)_(b)SiO_((4−a−b)/2)   (I)

[0020] where R=a C₂-C₈-alkenyl [and/]or unsaturated C₃-C₁₀-etherradical, such as, e.g. vinyl, allyl, 1-butenyl, 1-hexenyl or—CH₂—CH₂CH₂OCH₂CH═CH₂ etc.,

[0021] R¹=monovalent, saturated, optionally substituted hydrocarbonradicals with up to 10 carbon atoms from the group consisting ofsubstituted and unsubstituted alkyl, aryl and arylalkyl radicals,wherein a and b are integers within the following limits: 0≦a ≦3 or0≦b≦3 and 0≦a+b≦4 and each individual R or R¹ within the molecule may bethe same or different than any other R or R¹ within the molecule.

[0022] R is preferably vinyl or allyl, and particularly preferablyvinyl.

[0023] Examples of R¹ are methyl, ethyl, propyl, isopropyl, butyl, octyletc., cyclobutyl, cyclopentyl, cyclohexyl etc., phenyl, tolyl, xylyl,naphthyl etc., benzyl, phenylethyl, phenylpropyl. In one embodiment ofthe invention, some or all of the hydrogen atoms of alkyl, aryl andarylalkyl radicals R¹ are substituted by fluorine and/or chlorine,bromine or iodine atoms and/or cyano radicals. In this case, R¹corresponds, for example, to chloromethyl, trifluoropropyl,chlorophenyl, dibromophenyl, β-cyanoethyl, β-cyanopropyl orγ-cyanopropyl radicals. In preference, however, at least 90% of theradicals R¹ are methyl.

[0024] In a preferred embodiment of the invention, a equals 0 or 1.

[0025] Using nomenclature familiar to the expert, namely M =(CH₃)₃SiO_(1/2), D = (CH₃)₂SiO_(2/2), T = (CH₃)SiO_(3/2), Q = SiO_(4/2),while T and Q are branching sites M^(Vi) = (CH₂═CH)(CH₃)₂SiO_(1/2) andD^(Vi) = (CH₂═CH)(CH₃)SiO_(2/2) the following examples may be given   for the component A):

[0026] In component A), between 0.05 and 10% of R are unsaturated,particularly preferably between 0.2 and 6% and more particularlypreferably 0.6 to 2% of component A). The viscosity of component A) ispreferably between 10 and 100000 mPas, particularly preferably 50-10 000mPas, at 25° C.

[0027] In a preferred embodiment of the invention, the component A) is abranched organopolysiloxanes wherein the ratio of the number ofdiorganosiloxy units (D units) to the number of branching sites is onaverage 15 and 40, therein at least one triorganosiloxy unit (M unit)and at most half of all the M units are free from unsaturated radicals,the remaining M units each bear only one unsaturated radical, and thecontent of unsaturated radicals is 0.1 to 1 mmol/g (0.6 to 2%).

[0028] The branching sites of component A) are preferablymonoorganosiloxy units, i.e. trifunctional siloxy units (T units), whichmay, however, also be replaced in some cases by tetrafunctional siloxyunits (SiO_(4/2) units, Q units). Those organopolysiloxanes are e.g.described in DE-A 43 28 652.

[0029] The end groups of the branched organopolysiloxane free fromunsaturated radicals have the function of an internal plasticiser. Theflexibility of the cross-linked film may be controlled by means of thenumber of end groups free from unsaturated radicals (M units).

[0030] Examples of the preferred component A) are compoundscorresponding to the formulae

T₅D₂₀₀M^(Vi) ₅M₂, T₇D₂₈₀M^(Vi) ₅M₄,

T₆D₁₈₀D^(Vi) ₂M^(Vi) ₄M₄ and/or T₈D₂₅₀M^(Vi) ₇M₃.

[0031] Branched organopolysiloxanes A) containing at least 2 unsaturatedhydrocarbon groups may be prepared by conventional methods, such as e.g.by hydrolysis of chlorosilanes followed by polymerisation with lowmolecular weight cyclic diorganopolysiloxanes.

[0032] The methyl hydrogen polysiloxane B) contains preferably unitscorresponding to the general formula

H_(c)(R²)_(d)SiO_((4−c−d)/2)   (II)

[0033] wherein R²=monovalent, saturated, optionally substitutedhydrocarbon radicals with up to 10 carbon atoms from the groupconsisting of substituted and unsubstituted alkyl, phenyl, phenylalkyland/or C₂-C₈ alkenyl radicals, wherein

[0034] c and d are integers with 0≦d≦3 and 0≦c≦2 and 0≦c+d≦4, preferably0≦c≦1.

[0035] The methyl hydrogen polysiloxanes B) are preferably linear. Atleast half of the D units have hydrogen atoms bound preferably directlyto silicon (H(CH₃)SiO groups). The number of groups containing hydrogenatoms bound directly to silicon is preferably between 70 and 85% of thebifunctional units.

[0036] The molar proportion of hydrogen atoms bound directly to asilicon atom in component B) may be chosen at will—within the context ofthe structural limitations mentioned above.

[0037] In component B), the molar proportion of hydrogen atoms bounddirectly to a silicon atom is preferably between 0.01 and 17 mmol,particularly preferably between 0.1 and 17 mmol and very particularlypreferably between 1 and 17 mmol per gram of component B). This meansthat preferably between 3 and 50% of the residues R and H, morepreferred 30 to 50%.

[0038] Examples of component B) are compounds corresponding to theformulae

M^(H) ₂D₁₀, M₂D₁₀D^(H) ₁₀, M^(H) ₂D^(H) ₂₀D₁₀,

M^(Vi) ₂D^(H) ₁₁ and/or M₂D^(Vi) ₃D^(H) ₈ where

M^(H)=H(CH₃)₂SiO_(1/2) and

D^(H)=H(CH₃)SiO_(2/2).

[0039] The components A) and B) lie preferably in a quantity ratio suchthat the molar ratio of hydrogen atoms bound directly to a silicon atom(SiH) in component B) to the unsaturated radicals (Si-vinyl) incomponent A) is between 0.05 and 20, particularly preferably between 0.5and 10 and very particularly preferably between 1 and 3.

[0040] The organopolysiloxane C) within the meaning of the presentinvention is preferably a polysiloxane containing units corresponding tothe general formula

(R¹)_(e)SiO_((4−e)/2)   (III)

[0041] wherein R¹ are monovalent, saturated, optionally substitutedhydrocarbon radicals with up to 10 carbon atoms selected from the groupconsisting of substituted and unsubstituted alkyl, phenyl and arylalkylradicals, which may be the same or different within the molecule, and emay be integers between 0 and 3.

[0042] Component C) is preferably a linear polydimethylsiloxaneend-capped with trimethylsiloxy groups. The use of such trimethylsiloxyend-capped polydimethylsiloxane with a viscosity of between 50 mm₂s⁻¹and 5000 mm²s⁻¹ is particularly preferred.

[0043] The catalyst from the platinum group (D) contains preferably theelements platinum, rhodium, iridium, nickel, ruthenium and/or palladiumin the elemental form, on a support substance or in the form of itscompounds. Platinum compounds or platinum complexes are preferred, suchas for example H₂PtCl₆, platinum-olefin complexes, platinum-alcoholcomplexes, platinum-vinylsiloxane complexes or elemental platinum on asupport substance such as, e.g. activated carbon, Al₂O₃ or SiO₂.Component D) is particularly preferably a platinum-vinylsiloxanecomplex. Said platinum-vinylsiloxane complexes then preferably have atleast 2 olefinically unsaturated double bonds in the siloxane. These aredescribed e.g. in U.S. Pat. No. 3,715,334.

[0044] The term siloxane in this context includes polysiloxanes, i.e.for example vinylpolysiloxanes.

[0045] The proportion of component D), based on the sum of all theconstituents, is preferably between 1 and 1000 ppm, particularlypreferably between 1 and 500 ppm and very particularly preferablybetween 25 and 250 ppm.

[0046] The catalyst from the platinum group D) may also be dissolvedbeforehand, for example, in a part of the polymer A).

[0047] The term inhibitor E) within the meaning of the inventionincludes all the inhibitors known from the prior art, to prevent thatreaction occurs at room temperature when mixing components together andmaking sure a certain pot-life such as e.g. maleic acid and derivativesthereof, amines, alkylisocyanurates and acetylenically unsaturatedalcohols, in which the OH group is bound to a carbon atom adjacent tothe C—C triple bond, as described in more detail e.g. in U.S. Pat. No.3,445,420. Component E) is preferably 2-methyl-3-butyn-2-ol,1-ethynylcyclohexanol and/or (±) 3-phenyl-1-butyn-3-ol. The quantity ofcomponent E) in the mixture is preferably 0.0001% to 5%, particularlypreferably 0.01% to 2% and very particularly preferably 0.1 to 1%, basedon the total weight of the mixture.

[0048] In principle, component F) includes all the emulsifiers and/orthickeners suitable for the formation and stabilisation of emulsions(compare e.g. McCutcheon's Detergents & Emulsifiers, InternationalEdition).

[0049] In the event that the emulsions according to the invention areused for the preparation of release coatings in the food sector,preferred emulsifiers are those that are mentioned in the FDARegulations 176.170 “Components of Paper and Paperboard”.

[0050] Examples of suitable emulsifiers and thickeners F) are:

[0051] C₈-C₂₂-alkyldimethylbenzylammonium chloride, preferably at most1.5%, sodium lauryl sulphate, preferably at most 0.5%, polyethyleneglycol ethers of monohydric aliphatic alcohols C₁₂-C₂₀ and C₂-C₉ alkylphenols, polyethylene glycol esters of natural fatty acids C₈-C₂₂ andvegetable oils, and/or partially acetylated polyvinyl alcohol with lessthan 20% acetyl groups and a K value of more than 40. The quantity ofemulsifiers and thickeners F) should preferably not exceed 10%, based oncomponents A), B) and C).

[0052] Suitable emulsifiers are, in addition:

[0053] carboxymethylcellulose, hydrolysed starches, alginates, casein,hard paraffin and wax dispersions, dispersions based on copolymers ofacrylic and methacrylic acid esters, butadiene and styrene, and/orpolyvinyl alcohol (viscosity of the 4% aqueous solution at 20° C. atleast 4 cP).

[0054] Polyvinyl alcohol in combination with sodium lauryl sulphate oralkyldimethylbenzylammonium chloride is particularly preferred.

[0055] Additives and auxiliary substances G) within the meaning of theinvention are e.g. polysiloxane resins based on building blockscorresponding to the general formulae (I) and (II), fillers such as e.g.diatomaceous earths, finely dispersed quartz flour, amorphous silicas,pyrogenic and/or precipitated silicas with a BET surface of 50 to 500m²/g. Fillers of this kind may be surface-modified e.g. withorganosilicon compounds. The modification may also be achieved duringincorporation in the polymer by the addition of e.g.hexamethyldisilazane or 1,3-divinyl-1,1,3,3-tetramethyldisilazane andwater.

[0056] Additives and auxiliary substances G) within the meaning of theinvention are also wetting agents which help to improve the wetting ofthe substrate with the emulsion. For example, polyether siloxanes(silicone surfactants) and/or fluorosurfactants are suitable for thispurpose. Bacteriostatic agents (e.g. formaldehyde-cleaving products) mayalso be included amongst the additives and auxiliary substances G).

[0057] Component G) or the sum of components G) is preferably less than5 wt. %, based on the weight of total mixture.

[0058] Demineralised or deionised water is preferred for the aqueousemulsion.

[0059] The aqueous emulsions according to the invention preferably havethe following constituents: as component A): T₈D₂₅₀M^(Vi) ₇M₃ as methylhydrogen polysiloxane M₂D^(H) ₃₀D₁₀ B): as organopolysiloxane C):polydimethylsiloxane with a viscosity of 1 000 mm²/s as catalyst D):Pt-vinylsiloxane complex as inhibitor E): ethynyl cyclohexanol asemulsifier and/or thickener F): polyvinyl alcohol optionally in com-bination with sodium lauryl sulphate as additives and/or auxiliarybacteriostatic agents and/or polyether substances G) siloxane

[0060] The invention also provides a process for the preparation of theemulsions according to the invention, according to which catalyst D) andoptionally organopolysiloxane A) and/or organopolysiloxane C) areemulsified in water and an emulsion of organopolysiloxane A), methylhydrogen polysiloxane B), organopolysiloxane C), inhibitor E),emulsifiers and/or thickener F) is prepared separately in water and thetwo emulsions are then stirred together.

[0061] Additional components G) may be added to the components A), B)and/or C) before emulsification or to one of the two emulsions afteremulsification.

[0062] Suitable items of equipment for achieving a suitable particlesize for the stability or emulsion are, e.g. high pressure homogenisers,colloid mills or the like.

[0063] If the molar ratio of SiH:Si vinyl provided for is taken intoaccount when preparing the emulsions, both emulsions can be adjusted toa silicone content of 40% in such a way that they have to be mixedtogether prior to use in a quantity ratio of 1:1. It is also possible,however, to prepare an emulsion which contains only the catalyst D),emulsifiers and/or thickener F) and water, and which is added to asecond emulsion of organopolysiloxane A), methyl hydrogen siloxane B),organosiloxane C), inhibitor E), emulsifiers and/or thickener F) andwater in a quantity that is sufficient to bring about the desiredcatalytic effect.

[0064] The invention also provides for the use of the emulsionsaccording to the invention for the preparation of an abhesive finish forflexible substrates.

[0065] Roller or knife applicators followed by a drying oven aresuitable for this purpose.

[0066] The examples below serve to illustrate the invention withoutlimiting its scope.

EXAMPLES OF EXECUTION Example 1

[0067] Component Description Quantity in wt. % A) T₈D₂₅₀M^(Vi) ₇M₃ 36.0B) M₂D^(H) ₃₀D₁₀ 2.9 C) Polydimethylsiloxane with a 1.0 viscosity of1000 mm²/s (Baysilone-Öl M 1000) E) Ethynyl cyclohexanol 0.1 F)Polyvinyl alcohol Mowiol 4-88 3.0 Sodium lauryl sulphate 0.1 G)Bacteriostatic agent Preventol D2 0.1 from Bayer AG Water 56.8

Preparation of Emulsion

[0068] Components F) were dissolved in distilled water at a temperatureof 40° C. Components A), B), C), E) and G) were stirred together in aseparate preparation vessel and then stirred as a mixture into thesolution of component F) using a high-speed stirrer. The pre-emulsionthus obtained was homogenised in 5 passes at a pressure of 200 bar in ahigh-pressure homogeniser.

Example 2

[0069] Component Description Quantity in wt. % A) As in Example 1 32.7C) As in Example 1 1.0 D) Pt-vinyl siloxane complex 6.3 dissolved inpolymer A with 1320 ppm platinum F) As in Example 1 3.0 + 0.1 G) As inExample 1 0.1 Water 56.8

[0070] The emulsion was prepared as in Example 1, except with theabove-mentioned components.

Example 3 Procedure for Coating Baking Paper

[0071] The emulsion components from Examples 1 and 2 were mixed in aratio of 1:1 and diluted with water to approx. 10 wt. % activesubstance. This diluted emulsion mixture was applied to the paper to becoated and smoothed with a 10 mm metal knife. A similar procedure wasfollowed on the other side of the paper. Drying took place afterwards ina hot cabinet at 160° C. and with a 15 sec. residence time. The siliconecoating weight of the paper thus finished was then measured by x-rayfluorescence analysis. The coating weight in the case of theabove-mentioned dilution was between 0.4 g and 0.6 g of silicone/m².

Example 4

[0072] Baking test procedure Recipe:   4 eggs 1.5 dl wheat flour   1 dlpotato flour   1 dl sugar   1 teaspoon baking powder

[0073] All the ingredients were processed at room temperature. Eggs andsugar were beaten until frothy in 5 min. with a universal kitchenmachine on its highest speed setting, and the wheat flour, potato flourand baking powder were mixed together. The flour mixture was addedthrough a sieve to the egg-sugar froth and stirred with a spoon. Beforethe dough was prepared, the coated paper was folded into moulds whosebases measured 15×20 cm. Four of these folded moulds were placed on abaking tin. The quantity of dough was then divided evenly between thefour moulds. The dough was baked for 8 min. at 225° C. in a circulatoryoven. The finished baked product was turned out and cooled for 2 min. atroom temperature. The coated paper to be tested was then removed fromthe baked product.

[0074] Assessment: The quantity of baked product adhering to the paper,converted to g/m², was assessed. With the procedure according to Example3, 20 g of adhering baked product/m² were found.

Example 5

[0075] Component Description Quantity in wt. % A) As in Example 1 37.6B) As in Example 1 1.0 C) As in Example 1 1.0 E) As in Example 1 0.1 F)Polyvinyl alcohol Mowiol 4-88 3.0 Sodium lauryl sulphate 0.1 G)Polyether siloxane as wetting 0.3 agent (Baysilone Lackadditiv VP AI3468 from Bayer AG) Preventol D2 0.1 Water 56.8

Example 6

[0076] Component Description Quantity in wt. % C) As in Example 1 1.0 D)Pt-vinyl siloxane complex 49.0 dissolved in polymer A with 3400 ppmplatinum F) Mowiol 4-88 3.0 Sodium lauryl sulphate 0.1 G) Preventol D20.1 Water 46.8

Example 7 Procedure for Applying the Emulsion in the Laboratory

[0077] 100 g of the emulsion from Example 5 and 3 g of the emulsion fromExample 6 were diluted to 10% active substance; the subsequent procedurewas the same as in Example 3.

Example 8 Baking Test Procedure

[0078] Using a similar procedure as in Example 4, 18 g of baked productresidue/m² were found.

Example 9

[0079] (Not According to the Invention)

[0080] Preparation of a 40% silicone emulsion in the same way as Example1 without component C).

Example 10

[0081] (Not According to the Invention)

[0082] Preparation of a 40% silicone emulsion in the same way as Example2 without component C).

Example 11

[0083] Emulsion 9 and 10 were mixed and applied in the same way asExample 3.

Example 12

[0084] When the baking test was carried out in the same way as Example4, but using the mixed emulsions of example 11, 100 g of bakingresidue/m² were found.

1. Aqueous emulsions consisting essentially of: at least oneorganopolysiloxane A) containing at least 2 unsaturated hydrocarbongroups, at least one methyl hydrogen polysiloxane B), at least oneunreactive organopolysiloxane C), at least one catalyst D) from theplatinum group, at least one inhibitor E), optionally, emulsifiersand/or thickeners F), optionally, additives and/or auxiliary substancesG).
 2. Aqueous emulsions according to claim 1, wherein theorganopolysiloxane A) containing at least 2 unsaturated hydrocarbongroups is a cyclic, linear or branched polysiloxane which contains unitscorresponding to the general formula (I) (R)_(a)(R¹)_(b)SiO_((4−a−b)/2)  (I) where R=a C₂-C₈-alkenyl or an unsaturated C₃-C₁₀-ether radical andeach R within one of said units of formula G) can be the same ordifferent than any other R within said unit, R¹=monovalent, saturated,optionally substituted hydrocarbon radicals with 1 to 10 carbon atomsfrom the group consisting substituted and unsubstituted alkyl, phenyland phenylalkyl radicals, wherein a and b are integers within thefollowing limits: 0≦a≦3, 0≦b≦3 and 0≦a+b≦4 and each individual R and R¹within the molecule may be the same or different.
 3. Aqueous emulsionsaccording to claim 1 or 2, wherein the organopolysiloxane A) containingat least 2 unsaturated hydrocarbon groups comprises diorganosiloxy units(D units) and triorganosiloxy units (M units) is branched and the ratioof the number of diorganosiloxy units (D units) to the number ofbranching sites is on average 15 and 40, at least one triorganosiloxyunit (M unit) and at most half of all the M units are free fromunsaturated radicals, the remaining M units each bear only oneunsaturated radical, and the content of unsaturated radicals is 0.05 to10% .
 4. Aqueous emulsions according to claim 1 or 2, wherein the methylhydrogen polysiloxane B) contains units corresponding to the generalformula H_(c)(R²)_(d)SiO_((4−c−d)/2)   (II)wherein R²=monovalent,saturated, optionally substituted hydrocarbon radicals with 1 to 10carbon atoms selected from the group consisting of substituted andunsubstituted alkyl phenyl, phenylalkyl and/or C₂-C₈ alkenyl radicals,wherein c and d are integers with 0≦d≦3 and 0≦c≦2 and 0≦c+d≦4. 5.Aqueous emulsions according to claim 1 or 2, wherein the methyl hydrogenpolysiloxane B) is linear.
 6. Aqueous emulsions according to claim 1 or2, wherein in the methyl hydrogen polysiloxane B) the proportion ofhydrogen atoms bound directly to a silicon atom is between 3 and 50 mmolper gram of the methyl hydrogen polysiloxane B).
 7. Aqueous emulsionsaccording to claim 1 to 2, wherein the components A) and B) are presentin a quantity ratio such that the molar ratio of hydrogen atoms bounddirectly to a silicon atom (SiH) in component B) to the unsaturatedradicals (Si-vinyl) in component A) is between 0.05 and
 20. 8. Aqueousemulsions according to claim 1 or 2, wherein component C) is apolysiloxane containing units corresponding to the general formula (III)(R¹)_(e)SiO_((4−e)/2)   (III)wherein R¹=monovalent, saturated,optionally substituted hydrocarbon radicals with 1 to 10 carbon atomsfrom the group consisting of substituted and unsubstituted alkyl, phenyland phenylalkyl radicals which may be the same or different within themolecule, and e may be integers between 0 and
 3. 9. Aqueous emulsionsaccording to claim 1 or 2, wherein component D) is a catalyst whichcontains the elements platinum, rhodium, iridium, nickel, ruthenium[and/]or palladium in the elemental form or mixtures thereof, on asupport substance, or in the form of their compounds.
 10. Aqueousemulsions according to claim 1 or 2, wherein component E) is2-methyl-3-butyn-2-ol, 1-ethynylcyclohexanol, (±) 3-phenyl-1-butyn-3-olor mixture thereof.
 11. Aqueous emulsions according to claim 1 or 2,wherein component F) is C₈-C₂₂-alkyldimethylbenzylammonium chloride,sodium lauryl sulphate, polyethylene glycol ethers of monohydricaliphatic alcohols C₁₂-C₂₀ and C₂-C₉-alkylphenols, polyethylene glycolesters of natural fatty acids C₈-C₂₂ and vegetable oils, partiallyacetylated polyvinyl alcohol with less than 20% acetyl groups and a Kvalue of more than 40, or mixtures thereof.
 12. Aqueous emulsionsaccording to claim 1 or 2, wherein the additives and auxiliarysubstances G) are polysiloxane resins based on building blockscorresponding to the general formulae (I) and (II), fillers, flowpromoters, polyether siloxanes, fluorosurfactants, bacteriostatic agentsor combinations thereof.
 13. Aqueous emulsions according to claim 1 or2, comprising: as component A): T₈D₂₅₀M^(Vi) ₇M₃ as methyl hydrogenpolysiloxane B): M₂D^(H) ₃₀D₁₀ as organopolysiloxane C):polydimethylsiloxane with a viscosity of 1 000 mm²/s as catalyst D):Pt-vinylsiloxane complex as inhibitor E): ethynyl cyclohexanol asstabiliser and/or thickener F): polyvinyl alcohol optionally incombination with sodium lauryl sulphate as additives and/or auxiliarybacteriostatic agents and/or substances G) polyether siloxane.


14. A process for the preparation of aqueous emulsions according toclaim 1 or 2, wherein catalyst D) and optionally organopolysiloxane A)or organopolysiloxane or both are emulsified in water and an emulsion oforganopolysiloxane A), methyl hydrogen polysiloxane B),organopolysiloxane C), inhibitor E), optionally emulsifiers and/orthickener F) is prepared separately in water, and both emulsions arethen stirred together.
 15. An abhesive finish for flexible substratescomprising an emulsion according to claim
 1. 16. A coated flexiblesubstrate having a coating formed by applying the emulsion of claim 1 tothe substrate, and then drying.